<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">

<html>
<head>

<title>
PRISM Manual | ConfiguringPRISM / OtherOptions 
</title>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<meta name="keywords" content="prism, probabilistic, symbolic, model, checker, verification, birmingham, oxford, parker, norman, kwiatkowska">

<link rel="icon" href="../pub/skins/offline/images/p16.ico" type="image/x-icon">
<link rel="shortcut icon" href="../pub/skins/offline/images/p16.ico" type="image/x-icon">

<!--HTMLHeader--><style type='text/css'><!--
  ul, ol, pre, dl, p { margin-top:0px; margin-bottom:0px; }
  code.escaped { white-space: nowrap; }
  .vspace { margin-top:1.33em; }
  .indent { margin-left:40px; }
  .outdent { margin-left:40px; text-indent:-40px; }
  a.createlinktext { text-decoration:none; border-bottom:1px dotted gray; }
  a.createlink { text-decoration:none; position:relative; top:-0.5em;
    font-weight:bold; font-size:smaller; border-bottom:none; }
  img { border:0px; }
  .editconflict { color:green; 
  font-style:italic; margin-top:1.33em; margin-bottom:1.33em; }

  table.markup { border:2px dotted #ccf; width:90%; }
  td.markup1, td.markup2 { padding-left:10px; padding-right:10px; }
  table.vert td.markup1 { border-bottom:1px solid #ccf; }
  table.horiz td.markup1 { width:23em; border-right:1px solid #ccf; }
  table.markup caption { text-align:left; }
  div.faq p, div.faq pre { margin-left:2em; }
  div.faq p.question { margin:1em 0 0.75em 0; font-weight:bold; }
  div.faqtoc div.faq * { display:none; }
  div.faqtoc div.faq p.question 
    { display:block; font-weight:normal; margin:0.5em 0 0.5em 20px; line-height:normal; }
  div.faqtoc div.faq p.question * { display:inline; }
   
    .frame 
      { border:1px solid #cccccc; padding:4px; background-color:#f9f9f9; }
    .lfloat { float:left; margin-right:0.5em; }
    .rfloat { float:right; margin-left:0.5em; }
a.varlink { text-decoration:none; }

.sourceblocklink {
  text-align: right;
  font-size: smaller;
}
.sourceblocktext {
  padding: 0.5em;
  border: 1px solid #808080;
  color: #000000;
  background-color: #f1f0ed;
}
.sourceblocktext div {
  font-family: monospace;
  font-size: small;
  line-height: 1;
  height: 1%;
}
.sourceblocktext div.head,
.sourceblocktext div.foot {
  font: italic medium serif;
  padding: 0.5em;
}

--></style>  <meta name='robots' content='index,follow' />


<link type="text/css" rel="stylesheet" href="../pub/skins/offline/css/base.css">
<link type="text/css" rel="stylesheet" href="../pub/skins/offline/css/prism.css">
<link type="text/css" rel="stylesheet" href="../pub/skins/offline/css/prismmanual.css">

</head>

<body text="#000000" bgcolor="#ffffff">

<div id="layout-maincontainer">
<div id="layout-main">

<div id="prism-mainbox">

<!-- ============================================================================= -->

<!--PageHeaderFmt-->
<!--/PageHeaderFmt-->

<!--PageTitleFmt-->
  <div id="prism-man-title">
    <p><a class='wikilink' href='Introduction.html'>Configuring PRISM</a> /
</p><h1>Other Options</h1>

  </div>
<!--PageText-->
<div id='wikitext'>
<h3>Output options</h3>
<p>To increase the amount of information displayed by PRISM (in particular, to display lists of states and probability vectors), you can use the "Verbose output" option (activated with comand-line switch <code>-verbose</code> or <code>-v</code>). To display additional statistics about MTBDDs after model construction, use the "Extra MTBDD information" option (switch <code>-extraddinfo</code>) and, to view MTBDD sizes during the process of reachability, use option "Extra reachability information" (switch <code>-extrareachinfo</code>).
</p>
<div class='vspace'></div><h3>Fairness</h3>
<p>Sometimes, model checking of properties for MDPs requires fairness constraints to be taken into account.
See e.g. [<a class='wikilink' href='../Main/References.html#BK98'>BK98</a>],[<a class='wikilink' href='../Main/References.html#Bai98'>Bai98</a>] for more information.
To enable the use of fairness constraints (for <code><strong>P</strong></code> operator properties), use the <code>-fair</code> switch.
</p>
<div class='vspace'></div><h3>Probability/rate checks</h3>
<p>By default, when constructing a model, PRISM checks that all probabilities and rates are within acceptable ranges (i.e. are between 0 and 1, or are non-negative, respectively). For DTMCs and MDPs, it also checks that the probabilities sum up to one for each command. These checks are often very useful for highlighting user modelling errors and it is strongly recommended that you keep them enabled, however if you need to disable them you can do so via option "do prob checks?" in the GUI or command-line switch <code>-noprobchecks</code>.
</p>
<div class='vspace'></div><h3>CUDD memory</h3>
<p>CUDD, the underlying BDD and MTBDD library used in PRISM has an upper memory limit.
By default, this limit is 204800 KB (200 MB).
If you are working on a machine with significantly more memory this and PRISM runs out of memory when model checking, this may help.
To set the limit (in KB) from the command-line, use the <code>-cuddmaxmem val</code> switch.
You can also change this setting in the GUI, but you will need to close and restart the GUI (saving the settings as you do) for this option to take effect.
</p>
<div class='vspace'></div><h3>Java memory</h3>
<p>The Java virtual machine (JVM) used to execute PRISM also has un upper memory limit.
Sometimes (for example if you are trying to load a model for which the PRISM code is extremely lengthy),
this limit will be exceeded and you will see an error of the form <code>java.lang.OutOfMemory</code>.
The current default limit for the Sun JVM is 64MB.
To resolve this problem, you can increase this memory limit.
On Unix, Linux or Mac OS X platforms, this is done by setting the environment variable PRISM_JAVAMAXMEM, for example (under a <code>tcsh</code> shell):
</p>
<div class='vspace'></div>
<div class='sourceblock ' id='sourceblock1'>
  <div class='sourceblocktext'><div class="shell"><span style="font-weight:bold;">setenv PRISM_JAVAMAXMEM 512m</span><br/>
<span style="font-weight:bold;">prism big_model.pm</span><br/>
</div></div>
  <div class='sourceblocklink'><a href='OtherOptions@action=sourceblock&amp;num=1' type='text/plain'>[&#036;[Get Code]]</a></div>
</div>

<p class='vspace'>or (under a <code>bash</code> shell):
</p>
<div class='vspace'></div>
<div class='sourceblock ' id='sourceblock2'>
  <div class='sourceblocktext'><div class="shell"><span style="font-weight:bold;">PRISM_JAVAMAXMEM=512m</span><br/>
<span style="font-weight:bold;">export PRISM_JAVAMAXMEM</span><br/>
<span style="font-weight:bold;">prism big_model.pm</span><br/>
</div></div>
  <div class='sourceblocklink'><a href='OtherOptions@action=sourceblock&amp;num=2' type='text/plain'>[&#036;[Get Code]]</a></div>
</div>

<p class='vspace'>The lower case <code>m</code> in <code>512m</code> denotes MB.
If you are running PRISM on Windows you will have to do this manually by modifying the <code>prism.bat</code> or <code>xprism.bat</code> scripts.
To set the memory to 512MB for example, replace <code>java</code> at the start of the last line in the appropriate script with <code>java -Xmx512m</code>.
</p>
<div class='vspace'></div><h3>Precomputation</h3>
<p>By default, PRISM's probabilistic model checking algorithms use an initial <em>precomputation</em> step which uses graph-based techniques to efficient detect trivial cases where probabilities are 0 or 1. This can often result in improved performance and also reduce round-off errors. Occasionally, though, you may want to disable this step for efficiency (e.g. if you know that there are no/few such states and the precomputation process is slow). This can be done with the <code>-nopre</code> switch. You can also disable the individual algorithms for probability 0/1 using switches <code>-noprob0</code> and <code>-noprob1</code>.
</p>
<div class='vspace'></div>
</div>


<!--PageFooterFmt-->
  <div id='prism-man-footer'>
  </div>
<!--/PageFooterFmt-->


<!-- ============================================================================= -->

</div> <!-- id="prism-mainbox" -->

</div> <!-- id="layout-main" -->
</div> <!-- id="layout-maincontainer" -->

<div id="layout-leftcol">
<div id="prism-navbar2">

<h3><a class='wikilink' href='../Main/Welcome.html'>PRISM Manual</a></h3>
<p><strong><a class='wikilink' href='Introduction.html'>Configuring PRISM</a></strong>
</p><ul><li><a class='wikilink' href='Introduction.html'>Introduction</a>
</li><li><a class='wikilink' href='ComputationEngines.html'>Computation Engines</a>
</li><li><a class='wikilink' href='IterativeNumericalMethods.html'>Iterative Numerical Methods</a>
</li><li><a class='selflink' href='OtherOptions.html'>Other Options</a>
</li></ul><p>[ <a class='wikilink' href='AllOnOnePage.html'>View all</a> ]
</p>


</div>  <!-- id="prism-navbar2" -->
</div> <!-- id="layout-leftcol" -->

</body>
</html>
